Problem:
Lab Automation equipment uses different reagents for sample processing and instrument cleaning through out the process. The application offers three distinct challenges to the design engineer. First, the bottles are interchangeable with unpredictable changing liquid compositions. Second, cross contamination between reagents has to be minimized, which prevents the use of a contact measurement solution. Third, the sensing solution has to be robust enough for inexperienced lab technician and maintenance personnel.

Solution:
Balluff capacitive sensors offer a solution for each of the challenges described above simultaneously. The sensor in this example is mounted inside of a plastic panel, creating streamlined instrument aesthetics. The unique nature of capacitive sensors allows for sensing liquids non-invasively through two separate plastic walls – the instrument wall and plastic reagent container.

Two discrete sensors can be employed. One sensor is for low-level indication, which will trigger a signal to the operator that the reagent is nearly empty and then a second low-low indication, which will finally shut-off the operation due to insufficient reagent supply.

Both discrete sensors will offer a significant cost saving for today’s instruments equipped with an analog load cell or dispense cycle counter. An analog system is inherently failure prone and expensive, whereas the cycle counters provide only an indirect level feedback. They cannot account for situation like bottle change-out, which requires manual counter resets.

Recommended sensors: SMARTLevel capacitive sensors

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